The invention relates to a locking device for a motor vehicle having a number of doors, a portable transmitter and a receiver, to be arranged on the motor vehicle, for a code of the transmitter, and a control device for driving locks of the doors.
Such locking devices are frequently used in contemporary motor vehicles and are known from the art. In this case, the transmitter to be carried by the driver of the motor vehicle transmits a code which is fed to the control device by the receiver and evaluated in said control device. After checking the code, the control device drives a central locking arrangement for the doors and frequently an immobilizer of the motor vehicle as well.
The known locking device has the disadvantage that, particularly in the case of vehicles that are not wholly observable, such as buses or delivery vehicles for example, it opens doors which are out of sight of the driver. The locking device becomes highly inconvenient as a result of this, since, in order to afford protection against theft, the doors have to be monitored for example in a costly fashion using mirrors or other persons.
The invention is based on the problem of providing a locking device of the introductory mentioned type such that the doors can reliably be driven in a particularly convenient manner, and the monitoring of the open doors by the person carrying the transmitter becomes particularly simple.
This problem is solved according to the invention wherein the control device has means for detecting the position of the transmitter and is provided for exclusively driving at least one of the locks provided in dependence on the position of the transmitter.
This configuration makes it possible to define doors that are to be driven by the control device in accordance with the position of the transmitter. As a result of this, in the case of a parcel service vehicle, for example, it is possible to unlock exclusively the driver""s door or the rear door or one of a plurality of lateral sliding doors or a combination of the doors. A person carrying the transmitter therefore has highly convenient access to the motor vehicle without having to monitor other doors.
In accordance with an advantageous development of the invention, the control device becomes particularly cost-effective if means for detecting the position of the transmitter have a plurality of antennas, and if the control device is adapted for evaluating the signals of the antennas for determining the position of the transmitter. In the simplest case, the control device merely has to identify the antenna which receives the signals from the transmitter.
In accordance with another advantageous development of the invention, the position of the transmitter can be determined particularly accurately if the antennas are configured as directional antennas.
The locking device according to the invention has a particularly low power consumption if the control device has a transmission antenna that is provided for generating a start signal with respect to the portable transmitter.
The transmitter could, for example, have an accumulator as its own power supply. However, constant checking of a charge state of the accumulator can be avoided, in accordance with another advantageous development of the invention, if the start signal is assigned an activation energy for the transmitter.
It is frequently undesirable for the code that activates the control device to be radiated continuously, since it could be recorded and copied or passed on. Improper recording of the code can be reliably avoided, in accordance with another advantageous development of the invention, if the transmitter has an actuating element for radiating a code.
The locking device according to the invention can be used in a simple manner for driving a plurality of locks if the portable transmitter has a plurality of code generators. By virtue of an appropriate arrangement of the code generators on different transmitters, the locking device according to the invention forms a particularly convenient system for the targeted release of locks by different persons. As a result of this, the driver of the motor vehicle can, for example, use the transmitter to deactivate an immobilizer of the motor vehicle and start the engine, while a passenger just has a code generator for opening the doors. Since a plurality of code generators are arranged on a single transmitter, it becomes unnecessary to search for the transmitter provided for the envisaged application.
In accordance with another advantageous development of the invention, the portable transmitter becomes particularly cost-effective if it has a passive code generator with a stored code.
In accordance with another advantageous development of the invention, copying the code can be prevented in a simple manner if the portable transmitter has an active code generator for calculating a code after the start signal, containing a code, of the control device. By way of example, a microprocessor with a memory is suitable as the active code generator.
In accordance with another advantageous development of the invention, the monitoring of the doors by the person carrying the transmitter becomes particularly convenient if the control device is provided for locking the doors when the transmitter is removed from the reception range of the receiver.
In a locking device for a bus or for a transporter in which the doors are arranged on different sides it becomes particularly difficult to monitor those doors which are situated on the opposite side to the person carrying the transmitter. In the case of such buses, the monitoring becomes particularly convenient if the control device is provide for exclusively driving at least one of the doors present on the side of the transmitter. As a result of this, particularly in the case of coaches having a multiplicity of doors for luggage which are arranged on their long sides and are designed as flaps, the risk of theft can be kept particularly low.